Fixing structure for heat exchanger

ABSTRACT

A heat exchanger has a rectangular parallelepiped shape in which refrigerant flows. When sides configuring the heat exchanger having the rectangular parallelepiped shape include a first side, a second side, and a third side, a length of the third side is shortest. A surface surrounded by the first side and the second side is a heat exchange surface of the heat exchanger. A fixing structure for fixing the heat exchanger to a case includes at least one fixing portion disposed on at least one of a surface surrounded by the first side and the third side and a surface surrounded by the second side and the third side. The fixing portion is disposed at a position where a composite vibration mode of not greater than 1000 Hz is minimum.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2012-262209 filed on Nov. 30, 2012, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a fixing structure for a heat exchanger in which refrigerant flows.

BACKGROUND ART

Patent literature 1 describes a cooling evaporator in an air conditioning unit for a vehicle, and the cooling evaporator is mounted in an air conditioning unit case through elastic members at four corners of the evaporator. The elastic member absorbs vibration of the evaporator. When the vibration absorbing action will be described in more detail, the evaporator is coupled with a compressor in an engine compartment of the vehicle through a refrigerant piping, and the compressor is fitted to an engine of the vehicle and driven by the engine. For that reason, the compressor vibrates integrally with the engine. The compressor per se vibrates due to pulsation generated when the compressor discharges refrigerant. The vibration of the compressor propagates to the evaporator located within the vehicle interior through the refrigerant piping. Under the circumstances, the evaporator is supported by the elastic members whereby the vibration propagated to the evaporator is absorbed by the elastic members. The vibration of the evaporator is restrained from being transmitted to the air conditioning unit case, amplified, and becoming an abnormal noise (noise).

Patent literature 2 describes a heat exchanger in an air conditioning apparatus for a vehicle, in which non-passage components other than refrigerant passage are supported by a case. Since the non-passage components do not configure a flow path for heat exchange medium unlike the passage forming components, the non-passage components are not vibrated directly by the pulsation of the heat exchange medium, and also not vibrated directly by collision of the heat exchange medium. When the case supports portions not directly vibrated, the vibration of the heat exchanger is hard to be transmitted to the case.

PRIOR ART LITERATURES Patent Literature

-   Patent Literature 1: JP 2006-335189 A -   Patent Literature 2: JP 2012-1124 A

SUMMARY OF INVENTION

In the conventional art described in Patent literature 1, the elastic members intervene at the four corners. However, the elastic members mounted to the case of the evaporator increase the number of components producing the evaporator. This leads to an increase in the number of processes for manufacturing the evaporator, and leads to a reduction in the productivity.

In the conventional art described in Patent literature 2, the heat exchanger is constructed integrally with the non-passage components and the passage forming components while the non-passage components are supported. If the passage forming components vibrate, the vibration also propagates to the non-passage component. As a result, the effect of suppressing the transmission of the vibration is small, since the vibration propagates to the case.

The present disclosure aims at providing a fixing structure for a heat exchanger which is capable of reducing transmission of vibration to an external with a simple configuration.

According to the present disclosure, at least one fixing portion for being fixed to a case is disposed on at least one of a surface surrounded by a first side and a third side and a surface surrounded by a second side and the third side. In the fixing structure for a heat exchanger, the fixing portion is disposed at a position except for four corners of a heat exchange surface and except for a position corresponding to an antinode part of a natural vibration mode of the heat exchanger.

According to the present disclosure, the heat exchanger is fixed to the case disposed to the external. At least one fixing portion for being fixed to the case is disposed on at least one of the surface surrounded by the first side and the third side and the surface surrounded by the second side and the third side. Further, the fixing portion is disposed at the position except for the four corners of the heat exchange surface, and the position is also a position (hereinafter referred to as “position except for an antinode part”) except for a position corresponding to an antinode part of a natural vibration mode of the heat exchanger. It is difficult to vibrate at the position except for the four corners and except for the antinode part. In other words, the largest vibration occurs at the antinode part, and it is found by extensive research results of the applicant that the four corners are also positions to be liable to vibrate as with the antinode part. Since the fixing portion is disposed avoiding the position to be liable to vibrate, the heat exchanger is fixed to the case at a portion difficult to vibrate. This makes it difficult to propagate the vibration of the heat exchanger from the fixing portion to the case. The vibration from the heat exchanger to the case can be suppressed with a simple configuration to change the position of the fixing portion. As a result, noise caused by vibration transmitted to the case from the heat exchanger can be suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view illustrating an evaporator according to a first embodiment.

FIG. 2 is a diagram illustrating vibrating state in respective natural vibration modes.

FIG. 3 is a graph showing an amplitude in a longitudinal direction.

FIG. 4 is a front view illustrating a simplified evaporator.

FIG. 5 is a graph showing a relationship between a frequency and an inertance.

FIG. 6 is a graph showing a total inertance within a frequency band.

FIG. 7 is a front view illustrating an air conditioning apparatus for a vehicle according to a second embodiment.

FIG. 8 is a graph showing an amplitude in a width direction.

FIG. 9 is a front view illustrating an evaporator according to a third embodiment.

FIG. 10 is a front view illustrating an evaporator according to a fourth embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, multiple embodiments for embodying the present disclosure will be described with reference to the drawings. In each embodiment, parts corresponding to matters described in a preceding embodiment may be denoted by identical reference marks, or one character may be added to a preceding reference mark for abbreviating repetitive description. When a part of the configuration in the respective embodiments is described, other parts of the configuration are the same as those in the embodiment described precedently. Not only the combination of parts described specifically in the respective embodiments, but also the partial combination of the respective embodiments can be performed particularly if there is no harm in the combination.

First Embodiment

A first embodiment of the present disclosure will be described with reference to FIGS. 1 to 6. An evaporator 10 is a heat exchanger arranged in a refrigeration cycle not shown, in which refrigerant is compressed by a compressor to have high temperature and high pressure and is cooled by a radiator through heat radiation. Further, refrigerant is depressurized by a depressurizing device to have low temperature and low pressure, and the refrigerant is evaporated by the evaporator 10. As illustrated in FIG. 1, the evaporator 10 according to this embodiment includes a core portion 11, an upper tank unit 12, and a lower tank unit 13. The respective components are brazed to each other.

The core portion 11 is configured by alternately stacking multiple flat tubes 14 and multiple corrugated fins 15 on each other. A side plate 16 is arranged outside of the outermost corrugated fins 15 on both sides in a stacking direction thereof (X-direction in FIG. 1). A refrigerant which is an inner fluid of the core portion 11 flows along a longitudinal direction (Y-direction in FIG. 1) of the flat tubes 14. When it is assumed that a flowing direction of the refrigerant is a width direction Y of the evaporator 10, a ventilation direction in the core portion 11 is a thickness direction Z of the evaporator 10, and a direction (stacking direction) orthogonal to the width direction Y and the thickness direction Z is a longitudinal direction X of the evaporator 10. The evaporator 10 is arranged in a vehicle by setting the width direction Y as a vertical direction.

The flat tubes 14 are pipe members formed by bending a thin aluminum strip plate, and the cross-section orthogonal to the refrigerant flowing direction is formed in a flat shape. The flat tubes 14 may integrally define multiple refrigerant passages extending in the longitudinal direction through extrusion molding of an aluminum material. Alternatively, two metal thin plates made of aluminum may be joined together to have a hollow shape. A thickness of the flat tube 14 is, for example, 0.2 mm.

The corrugated fin 15 is formed by subjecting a thin aluminum strip plate having both surfaces on which a brazing filler metal is cladded in advance to roller processing in a meandering shape (wave shape). The corrugated fin 15 has multiple louvers (not shown) formed by cutting and bending for enhancing the heat exchange efficiency. A thickness of the corrugated fin 15 is, for example, 0.05 mm.

The side plate 16 is configured as reinforcing member on the core portion 11. The side plate 16 is formed by pressing an aluminum plate material that is a bare material on which a brazing filler metal is not cladded. Both ends of the side plate 16 in a longitudinal direction (width direction Y) are formed in a planar shape. A center portion of each side plate 16 is formed to have a U-shaped cross-section opened outward in the stacking direction of the flat tubes 14 and the corrugated fins 15. The side plate 16 is brazed to the corrugated fin 15. A thickness of the side plates 16 is, for example, 1 mm.

The upper tank unit 12 is divided into two in a longitudinal direction of the flat tube 14 to include a header plate adjacent to the flat tube and a header tank away from the flat tube. Each of the header tank and the header plate has a semi-circular or rectangular cross-sectional shape, and is formed by pressing an aluminum flat material.

A brazing filler metal is cladded on both surfaces of the header tank and an inner surface of the header plate in advance. The header tank and the header plate are fitted to each other, and brazed to form a cylindrical body in which two internal spaces are aligned in the flowing direction of the blowing air (thickness direction Z of the evaporator 10). A cap shaped by subjecting an aluminum flat material to press processing is brazed to an opening portion defined at an end of the upper tank unit 12 in a longitudinal direction thereof (both ends in the longitudinal direction X), thereby closing the opening portion. The thickness of the upper tank unit 12 and the lower tank unit 13 is, for example, 1 mm.

Further, two separators (not shown) are brazed substantially in the center of the upper tank unit 12 in the longitudinal direction X, and separate the respective internal spaces in the longitudinal direction of the upper tank unit 12 (longitudinal direction X of the evaporator 10). The two internal spaces of the upper tank unit 12 arrayed in the flowing direction of the blowing air communicate with each other through multiple communication passages not shown, in a region of the upper tank unit 12 on a right side of the separator.

The lower tank unit 13 has a structure similar to that of the upper tank unit 12, and forms a cylindrical body including a header tank and a header plate. A cap is provided at an opening portion on both ends thereof in the longitudinal direction. Unlike the upper tank unit 12, configurations corresponding to the separator and the communication passage are not provided in the lower tank unit 13.

A flat tube insertion port not shown and a side plate insertion port not shown are provided in a wall surface (wall surface of the header plate) of the upper and lower tank units adjacent to the core portion 11 at the same pitches as pitches of the flat tubes 14 and the side plates 16 in the longitudinal direction X. The end of the flat tube 14 in the longitudinal direction and the end of the side plate 16 in the longitudinal direction are inserted into the respective insertion ports, and brazed. With the above configuration, the flat tube 14 communicates with the internal space of the upper and lower tank unit 12, 13, and the ends of the side plate 16 in the longitudinal direction are supported and fixed to the upper and lower tank units 12 and 13 respectively.

A connection block 17 (refrigerant outlet/inlet part) is brazed to a left side end of the upper tank unit 12 in FIG. 1, and has an inlet port 18 into which refrigerant flows and an outlet port 19 out of which refrigerant flows. Of the internal spaces of the upper tank unit 12, the inlet port 18 communicates with inside of the tank unit 12 a on the downstream side in the air flow in FIG. 1 and the outlet port 19 communicates with inside of the tank unit 12 b on the upstream side in the air flow in FIG. 1.

The flat tubes 14 are arrayed in two rows so that the upstream flat tube row and the downstream flat tube row are aligned in a flow of blowing air which is an external fluid, in correspondence with the array of the upper and lower tank unit 12, 13. In the evaporator 10 formed as described above, after refrigerant flows into the tank unit 12 a from the inlet port 18 on the downstream side of the upper tank unit 12 in the air flow, the refrigerant makes a U-turn vertically and flows in the downstream flat tube row, and returns to a right region of the upper tank unit 12 in FIG. 1. The refrigerant flows from the upper tank unit 12 a (right tank unit) on the downstream side in the air flow into the upper tank unit 12 b (right tank unit) on the upstream side in the air flow. The refrigerant passes through the upstream flat tube row, makes a U-turn vertically in the same manner, and returns to the upper tank unit 12 b on the upstream side in the air flow. Then, the refrigerant finally flows out of the outlet port 19. During this operation, the evaporator 10 evaporates the refrigerant, thereby cooling the blowing air by latent heat of evaporation.

A fixing structure of the evaporator 10 will be described. The evaporator 10 is fixed into an air conditioning case configuring an air conditioning apparatus for a vehicle. The air conditioning case (not shown) includes an air ventilation passage therein, and an outside air inlet port and an inside air inlet port which are air intake ports are provided on one side of the ventilation passage. A blowing opening is defined on the other side of the ventilation passage, and the conditioned air is blown into the vehicle interior from the blowing opening. The air conditioning case is formed of multiple case members, and a material of the case member is, for example, a resin molded product such as polypropylene.

The evaporator 10 is arranged to cross the overall ventilation passage in the air conditioning case, and all of the blown air passes through the evaporator 10. The evaporator 10 described above functions as a heat exchanger that cools the blown air before flowing into a cold air passage by absorbing heat by the refrigerant flowing in the evaporator 10 during cooling operation.

As illustrated in FIG. 1, the evaporator 10 has a rectangular parallelepiped shape. When the evaporator 10 is viewed as the rectangular parallelepiped shape, it is assumed that a side of the evaporator 10 extending in the longitudinal direction X is a first side 31, a side of the evaporator 10 extending in the width direction Y is a second side 32, and a side of the evaporator 10 extending in the thickness direction Z is a third side 33. In this embodiment, a length of the first side 31 is longest, and a length of the third side 33 is shortest. Since a surface surrounded by the first side 31 and the second side 32 configures a surface of the core portion 11 and corresponds to a heat exchange surface 11 a in which heat is exchanged between the refrigerant and the air.

In this embodiment, a fixing structure of the evaporator 10 is configured by focusing attention on noise caused by vibration propagation from the evaporator 10 to the air conditioning case which is one of noise causes. Specifically, in order to suppress the vibration propagation from the evaporator 10 to the air conditioning case, attention is focused on the natural vibration mode of the evaporator 10 to configure the fixing structure.

The noise caused by the propagation from the evaporator 10 to the air conditioning case is restricted to 1000 Hz or lower. As illustrated in FIGS. 2 and 3, the evaporator 10 has the natural vibration mode in that frequency band, and the vibration manner is different depending on the vibration mode. In FIG. 3, a first order mode corresponds to 215 Hz. Likewise, a second order mode corresponds to 241 Hz, a third order mode corresponds to 367 Hz, a fourth order mode corresponds to 677 Hz, and a fifth order mode corresponds to 865 Hz. The axis of ordinate in FIG. 2 represents a dimensionless value with the maximum value of an amplitude as 1, which is called “vibration level”. The deflection illustrated in FIG. 2 is caused by the shape of the evaporator 10 regardless of physical properties.

The vibration exciting force of the vibration mode (sum of the vibration modes) is represented in FIG. 3, in portions where the amplitude is larger and portions where the amplitude is smaller are present on upper and lower sides, on front and rear sides, and on right and left sides. In order words, if a portion smallest in the sum of the vibration modes is held, the vibration transmission from the evaporator 10 to the air conditioning case can be minimized. Hereinafter, the large amplitude may be called “antinode” and the small amplitude may be called “node”.

In a conventional art, as indicated by imaginary lines 21 in FIG. 4, the evaporator 10 is held at four corners (square corners). In this holding method, because the antinode in the evaporator 10 is held, the vibration transmission from the evaporator 10 to the air conditioning case becomes large, and a reduction in NV (noise vibration) is insufficient. Therefore, in this embodiment, in order to reduce the NV, a structure is required to hold positions indicated by dashed lines 22 illustrated in FIG. 4.

Specifically, a fixing portion 30 for being fixed to at least one case is disposed on at least one of a surface surrounded by the first side 31 and the third side 33 (hereinafter also called “upper and lower surfaces”) and a surface surrounded by the second side 32 and the third side 33 (hereinafter also called “right and left surfaces”). In this embodiment, of the upper and lower surfaces, two fixing portions 30 are disposed on the lower surface. As shown in FIGS. 1 and 4, the fixing portion 30 is present at a position except for the four corners in the heat exchange surface 11 a of the evaporator 10 and except for a position corresponding to the antinode part (refer to FIG. 3) in the natural vibration mode of the evaporator 10. Therefore, the fixing portion 30 is arranged by avoiding center and both ends (four corners) of the first side 31. In other words, the fixing portion 30 is present at a position except for the above-mentioned four corners, such that the amplitude of the natural vibration mode of the evaporator 10 is smaller at the position than at the four corners.

Further, when a length of the first side 31 is defined as L, a preferable position of the fixing portion 30 is preferably a position apart by 0.25 L±0.05 L and a position apart by 0.75 L±0.05 L, from an end of the first side 31. In the present specification, 0.25 L means 0.25×L, and a case in which numbers and L are continuously described has the same manner meaning. In other words, the fixing portion 30 is disposed on at least one of a range of 0.2 L to 0.3 L and a range of 0.7 L to 0.8 L from the end of the first side 31. The positions of the fixing portion 30 correspond to regions surrounded by imaginary lines in FIG. 3. In other words, the fixing portion 30 is provided at the (so-called node) position where the composite vibration mode of not greater than 1000 Hz is minimum

The fixing portion 30 is defined by a protrusion portion protruding downward from the lower tank unit 13. The evaporator 10 is fixed to the air conditioning case in a state where the fixing portion 30 is pressed against an inner wall of the air conditioning case. An elastic member such as rubber is interposed between the fixing portion 30 and the air conditioning case. With the interposition of an elastic member, the vibration transmitted from the fixing portion 30 to the air conditioning case can be more attenuated. The evaporator 10 comes in contact with the air conditioning case in a portion other than the fixing portion 30, but is fixed to the air conditioning case at the fixing portion 30 to transmit the vibration. Therefore, the other contact portions come in contact with the air conditioning case to the degree of merely supporting the evaporator 10.

The fixing portion 30 is disposed at a position where a frequency of the vibration mode of the evaporator 10 is different from a natural frequency of a wall surface of the air conditioning case. The natural frequency of the air conditioning case is different depending on a location. If the fixing portion 30 is disposed at the position where the natural frequency of the air conditioning case is the same as the frequency of the vibration mode of the evaporator 10, even while the vibration transmitted from the evaporator 10 is attenuated, the air conditioning case largely vibrates. This is because the effect of reducing the NV becomes small.

Subsequently, experimental results will be described, which are obtained by comparing the fixing structure of the evaporator 10 according to this embodiment with a fixing structure of a comparative example. In the fixing structure of the embodiment, the evaporator 10 is fixed at the positions of 0.25 L and 0.75 L at each of the upper tank unit 12 and the lower tank unit 13. In the fixing structure of the comparative example, the evaporator is fixed at the four corners.

In experimenting, an expansion valve in addition to the evaporator are mounted to an air conditioning apparatus for a vehicle, and vibration is excited in the thickness direction Z relative to the expansion valve at nine kinds of respective frequencies shown in FIG. 5, that is, 160 Hz, 200 Hz, 250 Hz, 315 Hz, 400 Hz, 500 Hz, 630 Hz, 800 Hz, and 1000 Hz. In vibrating, Shaker (product name: integral shaker made by LMS International n.v.) is used.

The inertance is detected at a contact portion of the air conditioning case with the fixing portion 30 as a detection position by using a piezoresistive vibration acceleration sensor (Model No. 352C22 made by PCB). The experimental conditions in FIGS. 5 and 6 are identical with each other. FIG. 5 illustrates the inertances at the respective frequencies, and FIG. 6 illustrates a total of the inertances at 200 Hz to 1 kHz.

As illustrated in FIG. 5, it is found that the inertance is smaller in the embodiment than that is in the comparative example at all the frequencies. As a result, it is found that the effect of reducing the NV is larger in the embodiment compared with the comparative example. As illustrated in FIG. 6, the total of the inertances at 200 Hz to 1 kHz is smaller in the embodiment. Therefore, it is found that the effect of reducing the NV is larger in the embodiment compared with the comparative example. As is understood from FIGS. 5 and 6, it is apparent that the fixing structure of the evaporator 10 according to this embodiment has the effect of reducing the NV.

As described above, the evaporator 10 according to this embodiment is fixed to the air conditioning case disposed externally. Two fixing portions 30 for fixing the evaporator 10 to the air conditioning case are disposed on the surface surrounded by the first side 31 and the third side 33. Further, the fixing portion 30 is disposed at the position except for the four corners of the heat exchange surface 11 a and except for the position corresponding to the antinode part of the natural vibration mode of the evaporator 10. The position except for the four corners and the antinode part is a position where vibration is difficult. In other words, the antinode part is the position that most vibrates, and the four corners are also liable to vibrate. Since the fixing portion 30 is provided with the avoidance of the positions where the vibration is easily generated, the evaporator is fixed to the air conditioning case at portions difficult to vibrate. This makes it difficult to transmit the vibration of the evaporator 10 to the air conditioning case through the fixing portion 30. With a simple configuration to change the position of the fixing portion 30, the vibration transmission from the evaporator 10 to the air conditioning case can be suppressed. As a result, the noise caused by vibration of the air conditioning case can be suppressed while the evaporator 10 vibrates.

In this embodiment, preferably, the fixing portion 30 is disposed at the position except for the four corners of the heat exchange surface 11 a such that the amplitude of the natural vibration mode of the heat exchanger is smaller at the position than the amplitude at the four corners. When the evaporator is fixed at the position smaller in the amplitude than the four corners, the vibration transmitted to the air conditioning case can be suppressed compared with the conventional art where the evaporator is fixed at the four corners. As a result, the effect of reducing the NV can be achieved.

The position at which the fixing portion 30 is disposed is more preferably a position at which the composite vibration mode of not greater than 1000 Hz becomes minimum. The noise caused by the propagation from the evaporator 10 to the air conditioning apparatus for a vehicle is limited to 1000 Hz or lower. Therefore, the evaporator is fixed at the position where the composite vibration mode of not greater than 1000 Hz is minimum, thereby being capable of further suppressing the vibration transmitted to the air conditioning case.

The fixing portion 30 is disposed at a position where a frequency of the vibration mode of the evaporator 10 is different from the natural frequency of a wall surface of the air conditioning case. The natural frequency of the air conditioning case is different depending on a location. If the fixing portion 30 is disposed at a position where the natural frequency of the air conditioning case is the same as the frequency of the vibration mode of the evaporator 10, even while the vibration transmitted from the evaporator 10 is attenuated, the air conditioning case largely vibrates. Therefore, the fixing portion 30 is disposed at a position where the frequency of the vibration mode of the evaporator 10 is different from the natural frequency of the wall surface of the air conditioning case, thereby being capable of restraining the effect of reducing the NV from being lowered due to the natural frequency of the air conditioning case.

Further, in this embodiment, when the length of the first side 31 is defined as L, the fixing portion 30 is disposed at a position apart by 0.25 L±0.05 L, and a position apart by 0.75 L±0.05 L from the end of the first side 31. As illustrated in FIG. 3, the position of 0.25 L and the position of 0.75 L are positions of nodes. Since the fixing portion 30 is disposed in the vicinity (±0.05 L) of the positions of the nodes, the effect of reducing the NV can be achieved as described above.

In other words, in this embodiment, for the purpose of reducing the NV in the air conditioning apparatus for a vehicle, attention is focused on the vibration mode of the evaporator 10, and the fixing position of the evaporator 10 is optimized to suppress the vibration propagation to the air conditioning apparatus. Specifically, the evaporator 10 is fixed at the position except for the vicinity of the antinode parts of the evaporator 10, thereby being capable of reducing the NV in the air conditioning apparatus. Because the transmission of a main vibration mode of the evaporator 10 to the air conditioning case can be suppressed by pressing the nodes of the evaporator 10, the NV can be reduced in the air conditioning apparatus for a vehicle.

Second Embodiment

A second embodiment of the present disclosure will be described with reference to FIGS. 7 and 8. FIG. 7 illustrates an air conditioning apparatus for a vehicle, and an evaporator 10A is illustrated as an element configuring the air conditioning apparatus. The evaporator 10A configuring the air conditioning apparatus illustrated in FIG. 7 is integrally provided with an expansion valve 40. The evaporator 10A is connected to an outflow side of the expansion valve 40 in a refrigeration cycle device, and a refrigerant depressurized by the expansion valve 40 flows into the evaporator 10A. In the present embodiment, the fixing portion 30 is disposed at six locations. The respective fixing portion 30 is configured by a protrusion portion, similarly to the first embodiment.

As illustrated in FIG. 7, the fixing portions 30 are disposed in each of an upper tank unit 12 and a lower tank unit 13 at positions apart by 0.25 L±0.05 L and positions apart by 0.75 L±0.05 L from an end of a first side 31. Since the positions of the fixing portions 30 in the first side 31 are the same as those in the first embodiment described above, the same operation and effects can be achieved.

Moreover, the fixing portions 30 are disposed on respective side plates 16 located on both ends in the longitudinal direction X. Specifically, when it is assumed that a length of a second side 32 is W, the fixing portions 30 are preferably disposed at positions apart from an end of the second side 32 by 0.5 W±0.05 W. In the present specification, 0.5 W means 0.5×W. Regarding the second side 32, as illustrated in FIG. 8, a position of 0.5 W is a position forming a node in the second side 32. Since the fixing portions 30 are disposed in the vicinity (±0.05 W) of the position of the node, the effect of reducing the NV can be achieved as with the position of the fixing portions 30 of the first side 31. In this embodiment, since the evaporator 10 is fixed at six locations in the outer periphery, the evaporator 10 can be more firmly fixed to the air conditioning case.

Third Embodiment

A third embodiment of the present disclosure will be described with reference to FIG. 9. In FIG. 9, a configuration of a fixing portion 30B is different from that in the evaporator 10 of the first embodiment. The fixing portion 30B of the evaporator 10B according to this embodiment is defined by a protrusion portion protruding outward from a lower tank unit 13 as described above. Further, the protrusion portion is covered with an elastic member, for example, an antivibration rubber.

The fixing portion 30B is configured integrally with the protrusion portion and the elastic member, thereby being capable of surely bringing the elastic member in contact with the air conditioning case. With the above configuration, the vibration transmitted from the fixing portion 30B to the air conditioning case can be further attenuated.

Fourth Embodiment

A fourth embodiment of the present disclosure will be described with reference to FIG. 10. In FIG. 10, the position of the fixing portion 30 is different from that in the evaporator 10 of the first embodiment described above. The positions of the fixing portions 30 according to this embodiment are disposed on respective side plates 16 located on both ends in the longitudinal direction X. Specifically, when it is assumed that a length of a second side 32 is W, the fixing portions 30 are preferably disposed at positions apart from an end of the second side 32 by 0.5 W±0.05 W (positions indicated by imaginary lines 21 in FIG. 10). Regarding the second side 32, as illustrated in FIG. 8, a position of 0.5 W is a position forming a node in the second side 32. Since the fixing portion 30 is disposed in the vicinity (±0.05 W) of the positions of the nodes, the effect of reducing the NV can be achieved.

OTHER EMBODIMENTS

Hereinbefore, the preferred embodiments of the present disclosure are described. However, the present disclosure is not intended to be limited to the embodiments described above, and various modifications can be made as long as they do not depart from the gist thereof.

The structures of the embodiments described above are merely examples and the scope of the present disclosure is not intended to be limited to the scope described above. The scope of the present disclosure is represented by the claims, and includes meanings equivalent to those of the claims, and all changes in the scope.

In the first embodiment described above, the fixing portions 30 are disposed at two locations, but is not limited to two locations, and at least one fixing portion 30 may be disposed on at least one of a surface surrounded by the first side 31 and the third side 33 and a surface surrounded by the second side 32 and the third side 33. Therefore, for example, the fixing portion 30 may be disposed on only the side plate 16.

In the first embodiment described above, the evaporator 10 configures the air conditioning apparatus for a vehicle, but is not limited to the vehicle, and the evaporator may configure a domestic air conditioning apparatus. The present disclosure is not limited to be applied to the evaporator, but may be applied to a radiator or a condenser if the heat exchanger has a rectangular parallelepiped shape in which refrigerant flows. 

What is claimed is:
 1. A fixing structure for fixing a heat exchanger to a case, the heat exchanger having a rectangular parallelepiped shape in which refrigerant flows, when sides configuring the heat exchanger having the rectangular parallelepiped shape include a first side, a second side, and a third side, a length of the third side is shortest, a surface surrounded by the first side and the second side is a heat exchange surface of the heat exchanger, wherein the fixing structure comprising: at least one fixing portion disposed on at least one of a surface surrounded by the first side and the third side and a surface surrounded by the second side and the third side, wherein the fixing portion is disposed at a position where a composite vibration mode of not greater than 1000 Hz is minimum, except for four corners of the heat exchange surface and except for a position corresponding to an antinode part of a natural vibration mode of the heat exchanger. 2.-4. (canceled)
 5. The fixing structure according to claim 1, wherein the fixing portion is disposed at the position where a frequency of a vibration mode of the heat exchanger is different from a natural frequency of a wall surface of the case. 